I've been running the SRAM PG-970 cassette this past season. The shifting has been pretty good, however, it's wearing faster than the Shimano cassettes I've used in the past. But at half the cost, I really don't care too much.
I just didn't think they shifted as well. Not as crisp. I have trashed one of each though. I actually don't like sram drive train stuff. I don't like the chains, they are not smooth to me. I don't like that the X0/X9 is not rapid rise. I would love to trade my sram for some XT pods and a RR rear deraileur even.
*I'm with Kanter on the gearing. Who the eff skips that much of a gap on 34 tooth cogs???
One more thing - I would like to try an IRD. I hear the mechanical disks are pretty nice, so the cassettes should have some nice points. I love my Interloc road frame. Lots of nice detail touches. They seem to be on the way to making a name for themselves. When I spoke with them on the phone, the rep was concerned that they aren't growing quickly enough, but the stuff I have seen should help that along. Not sure about the coating on the cassettes, but I would like to try one. They do a 28 tooth road cassette, in 10 speed even, so they will likely take off with that. I just hope they are nice quality.